The characteristic of current high-level routers is that the control and forwarding are separated. Generally speaking, the inner of a router may consist of an active master board (AMB), a standby master board (SMB), and a line card (LC). The AMB and the SMB both belong to the control plane, while the LC belongs to the forwarding plane. They are connected through a switch network. As shown in FIG. 1, it is a schematic view illustrating the structure of the conventional router. FIG. 1 shows routers A, B, and C. The process of transmitting a message from the router A to the router C is as follows: the LC 1 of the router B receives the message, e.g. a link state advertisement (LSA) message, sent from the router A; by looking up a forwarding table, when it is found out that the router C can be arrived by passing through the LC 2, the LC 1 transmits the message to the LC 2 by the switch network; and the LC 2 directly transmits the message to the router C. The AMB does not play any role in the forwarding process, and is only responsible for collecting routing information and issuing it to the LC. The LC is only responsible for rapidly forwarding the message. The LC can support different kinds of interfaces. The forwarding table on the LC is generated according to the routing information issued by the AMB.
The control plane running on the router consists of many routing protocols. The open shortest path first (OSPF) protocol is the most widely used one. The OSPF protocol is run to store all the neighbors with the state of Full into the link state advertisement (LSA) message as link information. By the reliable transmission of the protocol, all the routers on the network may include exactly the same link state database (LSDB) and all the routers may use the same arithmetic. The routing with no loops may be obtained by calculating the same LSDB.
Currently, with regard to the application of router, there exists a non-stop routing (NSR) technique. In other words, in order to increase usability of the router, key boards (commonly, master boards) are backuped in the way of 1+1, i.e. they are stored in the AMB and the SMB. Under normal circumstances, the AMB works and the SMB dose not work. When a failure occurs, the AMB may be restarted by switching. At the same time, the SMB becomes the AMB so as to reduce the influence of the failure to the service as much as possible. If switching time is expected to be short as much as possible, the SMB needs to store the data of the AMB as much as possible. The data includes the LSDB needed for generating routing. At the moment, the LSDB stored by the SMB is required to be synchronized with the LSDB before switching as much as possible. After the switching occurs, the SMB obtains a new routing table by calculating according to the existing LSDB, so as to prevent the switching process from affecting the neighbor or the amount of service flows.
Regarding the NSR technique, one solution for implementing synchronization of the LSDB is as follows: after the LC receives a LSA message, the LC transmits the LSA message to the AMB and the SMB, simultaneously. After the SMB receives the LSA message, the SMB does not process the LSA message temporarily but caches and stores the LSA message. After the AMB receives the LSA message, the AMB starts to process the LSA message and transmits the processing result of each LSA message to the SMB. The SMB processes the cached LSA message, according to the processing result of the AMB. Therefore, when the switching occurs, after the SMB becomes a new AMB, the SMB could know that all the cached messages may not be processed by the original AMB, and the new AMB may continue to process these cached LSA messages.
Although the above mentioned technique can implement synchronization of the LSDB, it is complicated. For example, there is a need to encode all the processing manner of the LSA message for management and perform backup for all the places where the LSA message performs branch processing. All modifications for processing the LSA message, e.g. modification of codes and so on, may affect the final characteristic of implementing the NSR.